The invention relates generally to light transmissive articles, and in particular to methods of controlling the optical properties of light transmissive articles.
Abbe number or the V-number of a light transmissive material is a measure of the dispersion of the material, where dispersion is defined as the variation of refractive index with wavelength. The Abbe number (V) of a material is defined as:
  V  =                    n        D            -      1                      n        F            -              n        C            where nD, nF and nC are the refractive indices of the material at the wavelengths of the Fraunhofer D-, F- and C-spectral lines (589.2 nm, 486.1 nm and 656.3 nm, respectively). Generally, materials having high values of Abbe number exhibit low dispersion. In terms of the refractive index of the material, materials with high refractive index generally have a lower Abbe number than materials with low refractive index. Typical values of Abbe number range from around 20 for very dense flint glasses, to up to 65 for very light crown glass, and up to 85 for fluor-crown glasses.
Commercial optical applications are typically constrained to use materials that have a range of properties from low Abbe number and high refractive index material, to high Abbe number and low refractive index materials. Materials with low Abbe number and low refractive index are expensive and are difficult to obtain and therefore their usage is limited. It is desirable to provide a material with low Abbe number and low refractive index and methods of making the same.